Knights and Barbarians is a total conversion mod for Age of Empires III and both its expansions. The mod takes Age of Empires III back to the medieval ages, recounting Charles the Great, who made a German nation the biggest empire in Europe, with violent but discovering Vikings, to battling kingdoms in the Holy Land. Command armies from one of fourteen medieval powers in detailed, intense battles to defend or expand your kingdom. New content includes unique gameplay mechanics, units, factions, maps, music, and much more.

The Prologue version of Knights and Barbarians will focus on five factions: the Byzantine Empire (Byzantines), Republic of Venice (Italians), Salah-al-Din's Dominions (Saracens), the Seljuk Sultanate and Ottoman Empire (Turks) and the Kingdom of Jerusalem (Crusaders)

Later versions will also include the Kingdoms of England and Wales (English), House of Valois (French), Duchy of Flanders (Flemish), Kingdom of Denmark (Vikings), Holy Roman Empire (Germans), Kingdom of Poland and Grand Duchy of Lithuania (Slavs), Golden Horde (Mongols), Caliphate of Cordoba (Moors) and United Kingdom of Leon and Castille (Spanish)